Manufacture of phenol



y ,Patented Mu. 31, 1936v UNITED" STATES PATENT OFFICE 2,035,917, 4mirror-AdrURE oF PHENoL Application June 13, 1933, Serial No. 675,527

In Germany June 20, 1932 12 Claims.

-This invention relates to a process for the manufacture of phenol, andmore especially to a simplification and reduction of costs in themanufacture of phenol from benzene with vchlorobenzene as intermediateproduct.

' The main object of the invention is a new process for the productionof phenol from benzene by a hitherto unknown combination of a knownprocess for the production of chlorobenzene from benzene,hydrogen-chloride and air with the further known process for theproduction of phenol by hydrolysis of chlorobenzene.

A further object of the invention is a new process for the production ofphenol from benzene, 1;, in which as few. as possible by-products areobtained. f A further object of the invention is a new process for theproduction of phenol from benzene by using chlorobenzene, in which useis made go of the by-products obtained in one step of the process, andin which furthermore, use is made of the energies liberated in the otherstep of the process, which have no value for the purpose of said otherstep. v 2;, Further, it is the object of this invention to producephenol by means of a new process which results in only a very smallamount of by-products.

Processes are known for converting benzene no `into chlorobenzene by theaction of hydrogenchloride and air or oxygen. Processes are also knownfor hydrolizing chlorobenzene by the action of water vapor in thepresence of a catalyst so as to produce lphenol and hydrochloric 3:,acid.

l Since according to the equation CeH6-|-HC1+O=CsH5C1-{H2O in the firstprocess hydrogen chloride is con- 40 sumed and water is produced, whilstin the second process water is consumed and hydrochloric acid producedin accordance with the equation 4;, it should be possible theoreticallyby combining these two processes, as is seen by the equation resultingfrom the addition ofthe two forego- ;,0 ing equations, to provide theprocess for the manufacture of phenol from benzene which consumes nochemicals other than benzene and atmospheric oxygen and would thuspermit the production of phenol in an extraordinarily eco- 55 nomicalmanner.

It has not hitherto been possible to realize such a combined process inpractice, because in the known processes for making phenol thehydrogen-chloride which is produced and, in a combination of the tworeactions into a single proc- 5 ess, would have to be used again fortheproduction of chlorobenzene, is not obtained in a form in which itcan be further used, that is to say in the form of an aqueous solutionof a concentration which permits its use for making l0 chlorobenzene. Onthe contrary in all the known processes it is obtained in presence of somuch water that it would appear hopeless to attempt to isolate it in asumciently concentrated form and thus render it useful. In these knownprocl5 esses it was therefore neutralized directly after its productionby means of an alkaline substance, such as caustic soda solution, anoperation which would obviously exclude its further utilization for themanufacture of chlorobenzene.

There has recently become known aprocess which renders it possible torecover from the mixture of vapors resulting from the passage of thevapors of chlorobenzene and water over a catalyst at a raisedtemperature, by a suitable treatment, for example with a relativelysmall proportion of Water, the hydrogen-chloride in the form of aconcentrated solution; this process forms the subject of United Statesapplication Ser. No. 587,928 (filed January 21, 1932). Such a solutionis applicable for the production of chlorobenzene and thus permits thepossibility oficombining into a unitary process the two reactionshereinbefore referred to. This combination forms the subject of thepresent invention.

In the investigation of the combined process it was found that besidesthe advantages which were to be expected on theoretical grounds therearel also attained further technical advantages which were not to beexpected. l

(a) Firstly there is an economy in steam and cooling water required forevaporating and condensing the benzene.

When the phenol formed besides hydrogenchloride in the second stage isisolated by the process of the aforesaid speciilcation, it is obtainedin the form of an aqueous solution of about 8 per cent strength fromwhich it is isolated advantageously by extraction with a solvent. Thusthe `water containing phenol is advantageously extracted with benzene,the benzene then being separated by distillation from the phenolcontained in it. v

On the other hand for the production of chlorobenzene in the first stagea considerable quantity of benzene must4 be vaporized (compare Example 5of U. S. Patent No. 1,963,761).

Thus when the two processes are carried out independently a certainquantity of benzene must be vaporized and again condensed for thepurpose of isolating the phenol in the second stage, whilst an almostequally large quality of benzene must be vaporized in the first stagefor passage over the catalyst and condensed after passage over thecatalyst.

The combined process in accordance with the invention offers thepossibility of carrying out both the isolation of the phenol andtheproduction of the chlorobenzene with only a single evaporation andcondensation of the same quantity of benzene. For this purpose thebenzene which in the first stage is to be vaporized for the productionof chlorobenzene is previously used for the extraction of the phenolfrom its aqueous solution in the second stage; in this operation thebenzene contained in the solution of phenol in benzene is separated fromthe phenol'by evaporation and the benzene vapors thus obtained areintroduced, after having been suitably preheated, into the contactfurnace of the rst stage. The combination of the two processes thusattains the technical advantage that only about half the quantity ofsteam and cooling water is required for obtaining the same result aswould be obtained by conducting the two processes independently butotherwise in the same manner.

(b) Secondly the combined process permits a better utilization of theheat contained in the heating gases.

The most advantageous reaction temperature for the second stage, that isfor the conversion of chlorobenzene and steam into phenol andhydrogen-chloride, is about 500 C. After having separated the reactionproducts by means of the process of U. S. application Ser. No. 587,928led January 21, 1932 the mixture of the vapors of chlorobenzene andwater which have not reacted and are to be returned to the contactfurnace has a temperature of -100 C. The mixture is heated to thereaction temperature advantageously in part by heat exchange with thehot vapors leaving the furnace and having a temperature of about 500 C.,the temperature of the in-golng vapors being thus raised to about 400 C.The quantity of heat corresponding with the temperature difference of,for example, C. must be supplied to the vapors by means of furnacegases. The sensible heat of the furnace gases can thus be utilized onlyto an extent corresponding to the reduction of their temperature toabout 450 C., even if use were made of the counter-current principlewhich in this case is not advisable owing to the danger of over-heating.

In carrying out the process of the rst stage as described, for example,in U. Sq. Patent No. 1,963,761 it is necessary to raise the temperatureof the vapors of benzene and hydrochloric acid and air from about 100 toabout 250 C.

In the combination of the two processes this becomes possible withoutfurther expedients by using the heating gases of the second stage,having for example a temperature of 450 C., for preheating the vaporswhich are to react in the first stage. In practice this is most simplyconducted by heating the vapors for the two stages in a single furnaceand placing the heating pipes in which the vapor mixture of benzene andhydrochloric acid and the air are to be preheated behind the heatingpipes for heating the mixture of chlorobenzene and water vapors. In thismanner is attained the substantially better utilization of the heatcontained in the heating gases as hereinbefore referred to.

'I'he temperatures for carrying out the process of the production ofchlorobenzene should exceed C., preferably they do not exceed 300 C. Thetemperatures for carrying out the process of the production of phenolshould exceed 350 C., preferably they do not exceed 650 C.

. 'I'he special advantage of heat economy according to the abovestatements lies in the fact that the amounts of heat required by the twosystems in question correspond approximately to each other, especiallywhen carrying out the process under the best conditions (seethe abovementioned temperatures and the figures for the reacting quantities givenin the example beneath). Therefrom it results that for carrying out theprocess it is not necessary to apply additional heat to one or the othersystem.

(c) Finally the combination of the two processes renders it possible toavoid certain purification operations and their attendant losses.

The hydrochloric acid of about 17 per cent strength which is obtained inthe course of the separation of the reaction products of the secondstage according to the process of U. S. appli-- cation Ser. No. 587,928(led January 21, 1932) still contains small quantities of phenol whichis advantageously recovered by extraction with benzene. The hydrochloricacid retains after extraction small quantities of benzene which are notonly lost when the acid is 'used for some extraneous purpose but in manycases would be harmful to the use of the acid and in practice wouldtherefore have-to be removed, for example by boiling, by passage of acurrent of air, by absorption by means of active charcoal or otherwise,before the acid could be used. In the process of the present invention,in which the hydrochloric acid is used directly for the production ofchlorobenzene, not only is the presence of benzene harmless but thebenzene is not even lost, since already it constitutes a part of thebenzene which is to be brought to reaction with the hydrogen-chloride.

'I'hus by 'thecornbination of the two processes in accordance with theinvention complicated processes for purifying the hydrochloric acid andlosses of the benzene contained in it are avoided.

In the following quantitative example of a process for the production of10,000 kilos of phenol per day there is described one possibility ofcombining the two processes in accordance with the invention whilstmaking use of the aforesaid advantages. It must however be specificallystated that the invention is not limited to the procedure described inthe example or to the simultaneous utilization of all the advantageswhich it is possible to attain by the combination. In the followingexample reference is made to the accompanying drawing which showsdiagrammatically temperature of 500-C. and leaving the contact of theprocess, where they are heated to 500 C.

s,oas,e17 A t 3 ene :rem4 wmen'they pesa inte the contact mr- J nacejl.'f The mixture of vapors leaving the contact furnace 4 is cooled'to about200 C. in the heat recuperator 2 and then passes intoa washing g tower[constructed of acid-proof material, in which by the addition of 1,400'kilos of water and -1-,000 kilos of chlorobenzene (from a tank 20) 1perhour'the hydrogen-chloride is washed out and the chlorobenzene andwater consumed in the '1g reactionv are replacedin the circulatingmixture` y f "10.03." f 'lhevapors leaving thewashing tower l are ledinto a second washing tower l in which the j phenol .contained in themis removed by washing 1g with 8,000kilos of hot water (coming from Il)per hour. The excess of water and chlorobenzene introduced in theAwashing tower l pass in the form ofv vapor through thewashing'tower lto a [condenser 1 whilst the bulk oi' the vapors is zo 'again induced bythe blower I and returned to the cycle.

The hydrochloric acidy which runs off at the *base of ythe washing towerI is led into another washing tower l completely i'llled with liquid, 25from which it passes to a hydrochloric acid vaporizer 8. I

The solution of phenol whichruns of! at the y base of the washing tower5 at the rate of 400 kilos of phenol and 8,000 kilos of water per hour30 passes through a washing tower Il nlled with 'liquid and is pumped incirculation back into the washing tower 6. v Y s From a container ilthere are introduced per hour at the base of the washing tower 8, 600kilos :l5v of benzene and at the base of the washing tower Y I0, 4,000kilos of benzene; in the washing tower l the benzene extracts phenolcontained in the hydrochloric acid and in the washing tower I0 itextracts the phenol contained in the aqueous so- 4.oA lution. Thesolutions of phenol in benzene which leave the washingtowers I and Ilpass to a still I2 having a column, where the benzene is distllled. thevapors produced being passed through :the preheater 3. `After havingbeen suitably pre- 45 heated the benzene vapors, mixed with 1,400 kilosifof hydrochloric acid of 17 percent strength and '1,000 kilosof air per'hour are introduced by .means'ofa blower into a contact furnace Il inwhich lthe .benzene is chlorinated. 420 kilos of 50 'fphencl run on. perhour as residue from the still. y The chlorobenzene which is formed inthe con- '.tactfurnace I3 in quantity amounting to 550 kilos per hour is.advantageously recovered by fractional condensation lin a column Il andafter e., separationv from vwaterin the separating funnel .lBLandseparation from benzene and dichloro- 'benzene-in the still i1 with thecolumn Il re- .tothe system-by introduction into the j washing tower 5.Unchanged benzene passes in rmv the lform oi vapor from 'the column Ilinto a f 'and/'fed into the container Il.

Inv `this-mannerhy' a combination of two re- ;actionsgiwhich are'knownper se there is provided trial-procession the production ofphenolfrom benhydrocl'iloricy acid `which Yare converted into diprodueteed`:met 'therefore replaced,` there rojalie;"recuired no auxiliary.'chemicals either for the production or forthe isolation kof the productangeln? which, brrr-products are rj not obtained ingt'appreciable'quantitiea i K iThe t stage of reaction is carried out inthe presence of 'catalysts-lynch are-adapted to profndenser l5 where itis completely condensed f zene fin 'which,- Aapart from f smallquantities of emerebenzene somemere iugmy chlorinated duce chlorobenzenefrom a mixture of benzene,

nhydrochloric acid (hydrogen chloride) and air.

such as Vmixtures of a compound of copper and a catalytically activecompound oi `a metal of groups y3-8 ofthe periodic system. The second 5stage of the reaction is carried out in the presence of catalysts whichare adapted to aid the hydrolysis of the chlorobenzene in the vaporphase. such as catalysts containing chiefly catalytically active silicioacid or phosphates of metals of the second srOllD of the periodicsystem.

i. Process forthe production of-phenol comprisingA the reaction ofbenzene with hydrogenchloride and oxygen at temperatures exceeding 150C. to produce chlorobenzene, causing the latter to react at temperaturesexceeding 350 C. with steam in the vapor phase to produce phenol,utilizing the hydrogen-chloride resulting from the conversion ofthechlorobenzene into phenol for converting further quantity of benzeneinto chlorobenzene, the ilrst reaction being carried out in therpresenceof catalysts consisting of mixtures of a compound of copper and acatalyticalLv active compound of a metal of groups 3 '.'5 to 8 of theperiodic system, the second in presence of catalysts .promoting thehydrolysis of chlorobenzene in the vapor. phase.

2. Process for the production of phenol comprising the reaction ofbenzene with hydrogenchloride and oxygen at temperatures exceeding '150C. to produce chlorobenzene, causing the latter to react at temperaturesexceeding 3509 C. with steam in the vapor phase to produce phenol,utilizing the benzene which is to be converted into chlorobenzene atfirst for the extraction of phenol from the solution of phenol resultingfrom the hydrolysis of the chlorobenzene, the ilrst reaction beingcarried out in the presence of catalysts consisting of mixtures of acompound of 40 copper anda catalytically active compound of a metal ofgroups 3 to 8 of the periodic system, the second in presence ofcatalysts' promoting the hydrolysis of chlorobenzene in the vapor phase.

3. Process for'the production of phenol com- 45 prising the reaction ofbenzene with hydrogenchloride and oxygen at temperatures exceeding 150C. to produce chlorobenzene, causing the latter to react at temperaturesexceeding 350 C. with steam in the vapor phase to produce phenol,utilizing. the hydrogen-chloride resulting from the conversion ofthechlorobenzene into phenol for converting a further quantity of benzeneinto chlorobenzene, furthermore utilizing the benzene which is to beconverted into chlorobenzene' at 55 ilrst for the extraction of phenolfrom the solution of` phenol resulting from the hydrolysis ofthechlorobenzene. the ilrst reaction being carried out in the presenceof catalysts consisting of mixtures of a compound of` copper and acatalytically active compound of a metal of groups 3 to 8 of theperiodic system, the second in presence of catalysts promoting thehydrolysis of chlorobenzene inthe vapor phase.

4. Process forthe production of phenol comprising the reaction ofbenzene with hydrogenchlorideand oxygen at temperatures exceeding 150 C.to produce chlorobenzene, causing the latter to react at temperatuesexceeding 350 C. with steam in the vapor, phase toproduce phenol,utilizing the hydrogen-chloride resulting from the conversion ofthechlorobenzene into phenol for converting a yfurtherquantity orbenzeneinto chlorobenzene, the reactants for theproduction of thechlorobenzenebeing heated only by means n converting a further quantityof benzene into' of the waste heat contained in the heating gases usedin the conversion `of chlorobenzene into phenol, the firstreaction/being carried out in the presence of catalysts consisting ofmixtures of a compound of copper and a catalytically active 'compound ofa metal of groups 3 to 8 of the periodic system, the second in presenceof catalysts promoting the hydrolysis of chlorobenzene in the vaporphase. V

5.Process for the production of phenol comprising the reaction ofbenzene with hydrogenchloride and oxygen at temperatures exceeding 150C. to produce chlorobenzene, causing the latter to react at temperaturesexceeding 350 C. with steam in the vapor phase to produce phenol,utilizing the benzene which is to be converted into chlorobenzene at rstfor. the extraction of phenol from the solution of phenol resulting fromthe hydrolysis of the chlorobenzene, the

reactants for the production of the chlorobenzene being heated only bymeans of the waste heat contained in the heating gases used in theconversion of chlorobenzene intol phenol. the first reaction Abeingcarried out in the presence of catalysts consisting of mixtures of acompound of copper and a catalytically active compound of a metal ofgroups 3 to 8 of the periodic system, the second in presence ofcatalysts promoting the hydrolysis of chlorobenzene in the vapor phase.y 6. Process for the production of phenol consisting in the reaction ofbenzene with hydrogenchloride and oxygen at temperatures exceeding 150.C. to produce chlorobenzene," causing the latter to react attemperatures exceeding 350` C. with steam in the vapor phase to producephenol, utilizing the hydrogen-chloride resulting from the conversion ofthe chlorobenzene into phenol for chlorobenzene, furthermore utilizingthe benzene which is to be converted into chlorobenzene at ilrs't forthe extraction of phenol from the solution of phenol resulting from thehydrolysis of the chlorobenzene, the -reactants for the production ofthe chlorobenzene being heated only by means of the waste heat containedin the heatl ing gases used in the conversion of "chlorobenzene intophenol, the ilrst reaction being carried out in thepresence of catalystsconsisting'of mixtures of a compound of copper and a catalyticallyactive compound of a metal of groups 3 to 8 of the periodic system, thesecond in presence of catalysts promoting the hydrolysis ofchlorobenzene in the vapor phase.

7. Process for the production of phenol comprising the reaction cibenzene -with hydrogenchloride and oxygen at temperatures between 150and 300 C. to produce chlorobenzene, causing the latter to react attemperatures between 350 and 650 C. with steam in the vapor phase toproduce phenol, utilizing the hydrogen-chloride resulting from theconversion of theA chlorobenzene into phenol for converting a furtherquantity 'of benzene into chlorobenzene, the ilrst reaction beingcarried out in the presence of catalysts consisting o! mixtures of acompound o! copper and a catalytically active compound of a metal ofgroups 3 to 8 of the periodic system, the second in presence ofcatalysts promoting| the hydrolysis of chlorobenzene in the vapor phase.

8. Process for the production of phenol comprising the reaction ofbenzene with hydrogenchloride and oxygen at temperatures between 150 and300 C. to produce chlorobenzene, causing the latter to react attemperatures between 350 and 650 C; with steam in the -vapor phase toproduce phenol, utilizing the benzene which is to be converted intochlorobenzene at first for the extraction of phenol from the solution ofphenol resulting from the hydrolysis of the chlorobenzene,'the ilrstreaction being carried out in the presence of catalysts consisting ofmixtures of a compound of copper and a. catalytically active compoundoi' a metal of groups 3 to 8 of the periodic system, thesecond inpresence of catalysts promoting the hydrolysis oi' chlorobenzene in thevapor phase.

9. Process for the production of phenol comprising the reaction ofbenzene with hydrogenchloride and oxygen at temperatures between 150 and300 C. to produce chlorobenzene, causing the latter to react attemperatures between 350 y and 650 C. with steam in the vapor phase to amean of groups a to a of the periodic system,A

the second in presence ofcatalysts promoting the hydrolysis ofchlorobenzene in the vapor phase.

10. Process for the production of phenol comprising the reaction ofbenzene with hydrogenchloride and oxygen at temperatures between- 150and 300 C. to produce chlorobenzene, causing the latter to react attemperaturesvbetween 350 and 650 C. with steam in the vapor phase toproduce phenol, utilizing the hydrogen-chloride resulting from thevconversion of the chlorobenzene into phenol for converting a furtherquantity oi' benzene into chlorobenzene.' the reactants for theproduction of the chlorobenzene being heated only by means of the wasteheat contained in' the heating gases usedin the conversion ofchlorobenzene into phenol, the ilrst reaction being carried out in thepresence of catalysts consisting of mixtures oi' a compound of copperand a catalytically active compoundof a metal of groups 3 to 8 of theperiodic system, the second in presence of catalysts promoting thehydrolysis of chlorobenzene in the vapor phase. 11. Process for theproduction of phenol comprising the reaction of benzene withhydrogenchloride and oxygen at temperatures between 150 and 300 C. toproducechlorobenzene, causing the latter to react,at temperaturesbetween350 and 650 C. with steam in the vapor phase to produce phenol,utilizing the benzene which is to be converted into chlorobenzene at rstfor the extraction of phenol from the solution of phenol resulting fromthe hydrolysis of the chlorobenzene, the reactants for the production ofthe chlorobenzene being heated only by means o! the waste heat containedin the heating gases used in the conversion of chlorobenzene intophenol, the first reaction being carried outin the presence oi'catalysts consisting of mixtures of a compound of copper and acatalytically active compound of a metal of groups 3 to 8 of theperiodic system, the second in presence of catalysts promoting thehydrolysis of chlorobenzene in the vapor phase.

12. Process for the production of phenol comprising the reaction ofbenzene with hydrogen chloride and oxygen at temperatures between 150and 300 C. to produce chlorobenzene, causing the latter to react attemperatures between 350 and 650 C. with steam in the vapor phase toproduce phenol, utilizing the hydrogen-chloride resulting from theconversion ofthe chlorobenzene into phenol for converting a furtherquantity of benzene into chlorobenzene, furthermore utilizing thebenzene which is to be converted into chlorobenzene at rst for theextraction of phenol from the solution of phenol resulting from thehydrolysis of the chlorobenzene, the reactants for the production o! thechlorobenzene being heated only by means oi' the waste heat contained inthe heating gases used in the conversion of chlorobenzeneinto phenol.the rst reaction being carried out in the presence of catalystsconsisting of mixtures of a compound of copper and a catalyticallyactive compound oi a metal of groups 3 to 8 of the periodic system, thesecond in presence of catalysts promoting the hydrolysis ofchlorobenzene in the vapor phase.

WALTER PRAHL. WILHELM .'MA'l'HIIZ,v

CERTIFICATE CE CORRECTION. Patent No. 2,055,917. March 51, 1956.

- wALTER PRAHL, ET AL.

It is hereby certified that error appears vin the above numbered patentArequiring correction as follows z Throughout the drawing, in eachoccurrence in the legends for the misspelled words "benzine" .and"chlorobenzine" read benzene and chlorobenzene; and that the saidLetters Patient should be read with these corrections therein that theeamo may conform to the record of the case in the Patent Office.

-Signed and sealed this 19th day of October, A. D. 1957.

y Henry Van Arsdale. (Seal) Acting Commissioner of Patents.

